The past year prevalence of serious mental illness (SMI) was significantly higher among non-metropolitan than metropolitan (5.90% vs. 5.18%, P < .03) adults, and only 67.58% of non-metropolitan and 64.29% of metropolitan adults with SMI received any mental health treatment in the past year. Additional analyses revealed further non-metropolitan/metropolitan medication, inpatient, and outpatient treatment differences. Regardless of county type, unmet treatment needs remain. The most commonly reported barriers to receiving mental health treatment among persons with SMI were not knowing where to go, a fear of being committed/medicated, and not having time for treatment.